Magnetoresistance in granular magnetic tunnel junctions with Fe nanoparticles embedded in ZnSe semiconducting epilayer

We have investigated transport properties of iron (Fe) nanoparticles embedded in zinc selenide (ZnSe) semiconducting epilayers prepared by molecular beam epitaxy. Both positive and negative tunneling magnetoresistances (TMRs) were measured depending on the applied voltage biases and on the temperature. A slow reduction of the TMR magnitude with temperature was detected and it could be explained in terms of a crossover between direct/resonant tunneling and variable range hopping. The temperature behavior of the magnetoresistance is a clear signature of tunneling and hopping mechanisms mediated by the ZnSe barrier localized states. (C) 2008 American Institute of Physics.1031

Morphology of Au(1,1,1) vicinal surfaces studied by grazing incidence X-ray diffraction

6th International Conference on X-ray and Neutron Scattering, LEEWENHORST CONGRESS CTR, NOORDWIJKERHOUT, NETHERLANDS, SEP 12-17, 1999Two gold vicinal surfaces misoriented by 6 degrees, in opposite direction with respect to the (1,1,1) plane, namely the (4,5,5) and the(11,9,9) surfaces have been studied by grazing incidence X-ray diffraction. The main difference between these two surfaces is the step microscopic structure since the (4,5,5) surface presents \1,1,1\ like steps whereas the (11,9,9) surface exposes \1,0,0\ like steps, Two strongly different faceted morphologies are observed in good agreement with Scanning Tunneling Microscopy experiments. Surface reconstruction has also been extensively studied and our results open the way to understand the original faceting properties of gold vicinal surfaces. (C) 2000 Elsevier Science B.V. All rights reserved

HETEROEPITAXIAL GROWTH OF INAS ON GSAS(100) MEDIATED BY TE AT THE INTERFACE

The heteroepitaxy of InAs on a Te covered GaAs surface is investigated by photoelectron spectroscopy. Core-level spectra probed with synchrotron radiation show that Te remains at the interface between InAs and GaAs in a concentration much higher than the solubility limit of this element in III-V compounds, suggesting that a new compound is being formed. We propose that this interlayer is responsible for the observed changing in the growth mode of the InAs overlayer from islands to layer by layer

Thermal faceting behavior of Au(4,5,5)

The reversible Au(4,5,5) surface structure transformation has been followed by grazing incidence X-ray diffraction between 300 and 1000 K. At 300 K, the hill-and-valley morphology obtained after sputtering and annealing at a temperature above 800 K has been found to be in remarkable agreement with low energy electron diffraction and scanning tunneling microscopy studies. It consists of two orientational phases which are both Au(1,1,1) vicinal surfaces: the 4 degrees-phase which is reconstructed and the non-reconstructed 10 degrees-phase, The 4 degrees-phase presents a periodicity of 79 Angstrom, and the lines of discommensurations are perpendicular to the step edges. This result is consistent with the known interaction on the close-packed Au(111) surface between the reconstruction and the step edge atomic structures. The temperature dependence of the faceted morphology is found to be reversible and independent of the cooling rate, Between 550 and 1000 K, the 4 degrees-phase continuously increases its angle of misorientation and it is still reconstructed. On the other hand, the 10 degrees phase structure does not change its angle of misorientation within the temperature range, but decreases in intensity. (C) 1999 Elsevier Science B.V. All rights reserved

INDIUM-INDUCED LOWERING OF THE SCHWOEBEL BARRIER IN THE HOMOEPITAXIAL GROWTH OF CU(100)

We have investigated the effect of In on the homoepitaxial growth of Cu(100) by surface x-ray diffraction. We show that In enhances the interlayer transport by lowering the barrier for interlayer diffusion (Schwoebel barrier) at step edges. This effect is most pronounced for growth at low temperatures or when In is annealed on the surface before Cu deposition is started. Enhanced island nucleation cannot explain the smoother growth. The results are in agreement with recent calculations. We speculate that In also has a neutralizing effect on contaminants or defects

Electronic properties of embedded MnAs nano-clusters in a GaAs matrix and (Ga,Mn)As films: Evidence of distinct metallic character

We investigated the electronic properties of MnAs nano-clusters embedded in GaAs by bulk sensitive photoemission spectroscopy and cross-sectional scanning tunneling microscopy/spectroscopy. We report experimental evidences that the clusters are metallic MnAs, in close resemblance to MnAs thin films, and display a sharp interface with the surrounding GaAs. These results are supported by the comparison with GaMnAs and MnAs film in the same experimental condition. Furthermore, we observe a clear Coulomb blockade effect, as due to confinement and their nanometric size. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704778